Glucagon is a 29-amino acid pancreatic hormone which is secreted from the pancreatic a cells into the portal blood supply in response to hypoglycemia. It acts as a counterregulatory hormone to insulin. Most of the physiological effects of glucagon are mediated by its interaction with glucagon receptors in the liver, followed by activation of adenylate cyclase to increase intracellular cAMP levels. The result is an increase in glycogenolysis and gluconeogenesis, while attenuating the ability of insulin to inhibit these metabolic processes (Johnson et al., J. Biol Chem. 1972, 247, 3229-3235). As such, overall rates of hepatic glucose synthesis and glycogen metabolism are controlled by the systemic ratio of insulin and glucagon (Roden et al., J. Clin. Invest. 1996. 97, 642-648; Brand et al., Diabetologia 1994, 37, 985-993).
Diabetes is a disease characterized by elevated levels of plasma glucose. Uncontrolled hyperglycemia is associated with an increased risk for microvascular and macrovascular diseases, including nephropathy, retinopathy, hypertension, stroke, and heart disease. Control of glucose homeostasis is a major approach to the treatment of diabetes. It has been demonstrated in healthy animals as well as in animal models of types I and II diabetes that removal of circulating glucagon with selective and specific antibodies results in reduction of the glycemic level (Brand et al., Diabetologia 1994, 37, 985-993; Brand et al., Diabetes 1994. 43(Suppl. 1), 172A). Therefore, one of the potential treatments for diabetes and other diseases involving impaired glycemia is to block a glucagon receptor with a glucagon receptor antagonist to improve insulin responsiveness, to decrease the rate of gluconeogenesis, and/or to lower plasma glucose levels by reducing the rate of hepatic glucose output in a patient.
Glucagon antagonists are known, e.g., UA20040014789. UA20040152750A1, WO04002480A1, U.S. Ser. No. 06/881,746B2, WO03053938A1, UA20030212119. UA20030236292. WO03048109A1, WO03048109A1, WO00069810A1, WO02040444A1, U.S. Ser. No. 06/875,760B2, UA20070015757A, WO04050039A2. UA20060116366A1, WO04069158A2, WO05121097A2, WO05121097A2, WO07015999A2. UA20070203186A1, UA20080108620A1, UA20060084681A1, WO04100875A2, WO05065680A1, UA20070105930A1, U.S. Ser. No. 07/301,036B2, UA20080085926A1, WO08042223A1, WO07047177A1, UA20070088071A1, WO07111864A2, WO06102067A1, WO07136577A2, WO06104826A2, WO05118542A1, WO05123668A1, WO06086488, WO07106181A2, WO07114855A2, UA20070249688A1, WO07123581A1, WO06086488A2, WO07120270A2, WO07120284A2, and UA20080125468A1, although at this time none are commercially available as therapeutics. Not all compounds that are glucagon antagonists have characteristics affording the best potential to become useful therapeutics. Some of these characteristics include high affinity at the glucagon receptor, duration of receptor activation, oral bioavailability, and stability (e.g., ability to formulate or crystallize, shelf life). Such characteristics can lead to improved safety, tolerability, efficacy, therapeutic index, patient compliance, cost efficiency, manufacturing ease, etc. It has been unexpectedly discovered that specific stereochemistry and functional groups of the compounds of the present invention exhibit one or more of these desired characteristics, including markedly improved receptor binding properties, oral bioavailability, and/or other advantageous features that enhance their suitability for therapeutic use.
All documents referred to herein are incorporated by reference into the present application as though fully set forth herein.